docs: def get_fieldsets(self, request, obj=None):
          """
          Add fieldsets of placeholders to the list of already
          existing fieldsets.
          """
  
          # some ugly business to remove freeze_date
          # from the field list
          general_module = {
              'fields': list(self.general_fields),
              'classes': ('module-general',),
          }
  
          default_fieldsets = list(self.fieldsets)
          if not request.user.has_perm('pages.can_freeze'):
              general_module['fields'].remove('freeze_date')
          if not request.user.has_perm('pages.can_publish'):
              general_module['fields'].remove('status')
          if not len(registry):
              general_module['fields'].remove('delegate_to')
  
          default_fieldsets[0][1] = general_module
  
          placeholder_fieldsets = []
          section_placeholder_fieldsets = defaultdict(list)
          template = get_template_from_request(request, obj)
          for placeholder in get_placeholders(template):
              if placeholder.ctype not in self.mandatory_placeholders and not placeholder.section:
                  placeholder_fieldsets.append(placeholder.ctype)
              elif placeholder.section:
                  section_placeholder_fieldsets[placeholder.section].append(placeholder.ctype)
  
          additional_fieldsets = []
          for title, fieldset in section_placeholder_fieldsets.items():
              additional_fieldsets.append((title, {
                  'fields': fieldset,
                  'classes': ('module-content collapse grp-collapse grp-closed',),
              }))
          additional_fieldsets.append((_('Content'), {
              'fields': placeholder_fieldsets,
              'classes': ('module-content',),
          }))
          return default_fieldsets + additional_fieldsets